Jump to content

C 20

From Wikipedia, the free encyclopedia
C language revisions

C 20 is a version of the ISO/IEC 14882 standard for the C programming language. C 20 replaced the prior version of the C standard, called C 17, and was later replaced by C 23.[1] The standard was technically finalized[2] by WG21 at the meeting in Prague in February 2020,[3] had its final draft version announced in March 2020,[4] was approved on 4 September 2020,[5][6] and published in December 2020.[7]

Features

[edit]

C 20 adds more new major features than C 14 or C 17.[8] Changes that have been accepted into C 20 include:[9]

Language

[edit]
  • concepts,[10] with terse syntax[11]
  • modules[12]
  • designated initializers[13] (based on the C99 feature, and common g extension)
  • [=, this] as a lambda capture[14]
  • template parameter lists on lambdas[15]
  • three-way comparison using the "spaceship operator", operator <=>
  • initialization of an additional variable within a range-based for statement[16]
  • lambdas in unevaluated contexts[17][18]
  • default constructible and assignable stateless lambdas[17][19]
  • allow pack expansions in lambda init-capture[17][20]
  • class types in non-type template parameters, also allowing string literals as template parameters[21]
  • removing the need for typename in certain circumstances[22]
  • new standard attributes [[no_unique_address]],[23] [[likely]] and [[unlikely]][24]
  • conditional explicit, allowing the explicit modifier to be contingent on a Boolean expression[25]
  • expanded constexpr: virtual functions,[26] union,[27] try and catch,[28] dynamic_cast and typeid,[29] std::pointer_traits[30]
  • immediate functions using the new consteval keyword[31]
  • signed integers are now defined to be represented using two's complement (signed integer overflow remains undefined behavior)[32]
  • a revised memory model[33]
  • various improvements to structured bindings (interaction with lambda captures, static and thread_local storage duration)[34][35]
  • coroutines[36]
  • using on scoped enums[37]
  • constinit keyword[38]

Library

[edit]
  • ranges (The One Ranges Proposal)[39]
  • std::make_shared and std::allocate_shared for arrays[40]
  • atomic smart pointers (such as std::atomic<shared_ptr<T>> and std::atomic<weak_ptr<T>>)[41]
  • std::to_address to convert a pointer to a raw pointer[42]
  • calendar and time-zone additions to <chrono>[43]
  • std::span, providing a view to a contiguous array (analogous to std::string_view but span can mutate the referenced sequence)[44]
  • std::erase and std::erase_if, simplifying element erasure for most standard containers[45]
  • <version> header[46]
  • std::bit_cast<> for type casting of object representations, with less verbosity than memcpy() and more ability to exploit compiler internals[47]
  • feature test macros[48]
  • various constexpr library bits[49]
  • smart pointer creation with default initialization[50]
  • contains-method for associative containers[51]
  • bit operations, such as leading/trailing zero/one count,[52] and log2 operations[53][54][55]
  • std::bind_front[56]

New and changed keywords

[edit]

Many new keywords added (and the new "spaceship operator", operator <=>), such as concept, constinit,[38] consteval, co_await, co_return, co_yield, requires (plus changed meaning for export), and char8_t (for UTF-8 support).[57] And explicit can take an expression since C 20.[58] Most of the uses of the volatile keyword have been deprecated.[59]

In addition to keywords, there are identifiers with special meaning, including new import and module.

New attributes in C 20: [[likely]], [[unlikely]], and [[no_unique_address]][60]

Removed and deprecated

[edit]

Removed features:[61]

  • The C-derived headers <ccomplex>, <ciso646>, <cstdalign>, <cstdbool> and <ctgmath> were removed, as they serve no purpose in C . (The corresponding <*.h> headers remain, for compatibility with C.)
  • The use of throw() as an exception specification was removed.
  • Some previously deprecated library features were removed, including std::uncaught_exception, std::raw_storage_iterator, std::is_literal_type, std::is_literal_type_v, std::result_of and std::result_of_t.

Deprecated features:

  • Use of comma operator in subscript expressions has been deprecated[62]
  • (most of) volatile has been deprecated[59]

Published as Technical Specifications

[edit]
  • Parallelism TS v2[63] (including task blocks)
  • Reflection TS v1[64]
  • Networking TS v1[65]

Deferred to a later standard

[edit]
  • Contracts – a new study group (SG21) has been formed to work on a new proposal[66]
  • Reflection[67][68]
  • Metaclasses[69]
  • Executors[70]
  • Networking extensions,[71][72] including async, basic I/O services, timers, buffers and buffer-oriented streams, sockets, and Internet protocols (blocked by executors)
  • Properties[73]
  • Extended futures[74]

Compiler support

[edit]

Full support[75]

  • Visual Studio 2019 supports all C 20 features through its /std:c latest option, as of version 16.10.0.[76] An option /std:c 20 to enable C 20 mode is added in version 16.11.0.[77][78]

Microsoft's compiler supports not only Windows but also Linux, Android, and iOS. However, for Linux development, it requires the "Visual C for Linux Development" extension. [79]

Partial

  • Clang has partial C 20 support that can be enabled with the option -std=c 20 (version 10 and later) or -std=c 2a (version 9 and earlier).[80]
  • EDG started implementing C 20 features in version 5.0 and as of version 6.1 supports most C 20 core language features.[81]
  • GCC added partial, experimental C 20 support in 2017[82] in version 8 through the option -std=c 2a. Like Clang, GCC replaced this option with -std=c 20 in version 10. It also has an option to enable GNU extensions in addition to the experimental C 20 support, -std=gnu 20.[83]

History

[edit]

Changes applied to the C 20 working draft in July 2017 (Toronto) include:[84]

  • concepts (what made it into the standard is a cut-down version; also described as "Concepts Lite"[85])
  • designated initializers
  • [=, this] as a lambda capture
  • template parameter lists on lambdas
  • std::make_shared and std::allocate_shared for arrays

Changes applied to the C 20 working draft in the fall meeting in November 2017 (Albuquerque) include:[86][87]

  • three-way comparison using the "spaceship operator", operator <=>
  • initialization of an additional variable within a range-based for statement
  • lambdas in unevaluated contexts
  • default constructible and assignable stateless lambdas
  • allow pack expansions in lambda init-capture
  • string literals as template parameters
  • atomic smart pointers (such as std::atomic<shared_ptr<T>> and std::atomic<weak_ptr<T>>)
  • std::to_address to convert a pointer to a raw pointer

Changes applied to the C 20 working draft in March 2018 (Jacksonville) include:[88]

  • removing the need for typename in certain circumstances
  • new standard attributes [[no_unique_address]], [[likely]] and [[unlikely]]
  • calendar and time-zone additions to <chrono>
  • std::span, providing a view to a contiguous array (analogous to std::string_view but span can mutate the referenced sequence)
  • <version> header

Changes applied to the C 20 working draft in the summer meeting in June 2018 (Rapperswil) include:[89]

  • contracts (later deferred to a later standard)[90]
  • feature test macros
  • bit-casting of object representations, with less verbosity than memcpy() and more ability to exploit compiler internals
  • conditional explicit, allowing the explicit modifier to be contingent on a Boolean expression
  • constexpr virtual functions

Changes applied to the C 20 working draft in the fall meeting in November 2018 (San Diego) include:[91]

  • ranges (The One Ranges Proposal)
  • concept terse syntax
  • constexpr union, try and catch, dynamic_cast, typeid and std::pointer_traits.
  • various constexpr library bits
  • immediate functions using the new consteval keyword
  • signed integers are now defined to be represented using two's complement (signed integer overflow remains undefined behavior)
  • refinements of the contracts facility (access control in contract conditions)[92] (see list of features deferred to a later standard)
  • a revised memory model
  • smart pointer creation with default initialization

Changes applied to the C 20 working draft in the winter meeting in February 2019 (Kona) include:[93][94][95]

  • coroutines
  • modules
  • various improvements to structured bindings (interaction with lambda captures, static and thread_local storage duration)

Changes applied to the C 20 working draft in the summer meeting in July 2019 (Cologne) include:[96][97][98][99]

  • contracts were removed (see list of features deferred to a later standard)[100]
  • use of comma operator in subscript expressions has been deprecated[62]
  • constexpr additions (trivial default initialization,[101] unevaluated inline-assembly[102])
  • using scoped enums[37]
  • various changes to the spaceship operator[103][104]
  • DR: minor changes to modules[105]
  • constinit keyword
  • changes to concepts (removal of -> Type return-type-requirements[106])
  • (most of) volatile has been deprecated[59]
  • DR: [[nodiscard]] effects on constructors[107]
  • The new standard library concepts will not use PascalCase (rather standard_case, as the rest of the standard library)[108]
  • text formatting (std::format, [109][110] chrono integration,[111] corner case fixes[112])
  • bit operations[52]
  • constexpr INVOKE[113]
  • math constants[114]
  • consistency additions to atomics (std::atomic_ref<T>,[115] std::atomic<std::shared_ptr<T>>[116])
  • add the <=> operator to the standard library[117]
  • header units for the standard library[118]
  • synchronization facilities[119] (merged from: Efficient atomic waiting and semaphores,[120] latches and barriers,[121] Improving atomic_flag,[122] Don't Make C Unimplementable On Small CPUs[123])
  • std::source_location[124]
  • constexpr containers (std::string,[125] std::vector[126])
  • std::stop_token and joining thread (std::jthread)[127]

Changes applied during the NB comment resolution in the fall meeting in November 2019 (Belfast) include:[128][129][130][131]

  • Class Types in Non-Type Template Parameters (NTTP): The restriction of no user-defined operator== allowed has been removed as the meaning of template argument equality has been divorced from operator==.[132] This allows also for array members in class-type NTTP.
  • Floating-point types,[133] pointers and references and unions and union-like classes (class types containing anonymous unions) are now allowed as NTTP.
  • Function identity now also includes trailing requires-clauses (P1971)
  • Constrained non-template functions have been removed
  • <compare> is now available in freestanding implementations[134]
  • std::spans typedef was changed from index_type to size_type to be consistent with the rest of the standard library[135]
  • Concept traits have been renamed to follow the renaming of the concepts as a result from the Cologne meeting
  • Several fixes and additions to ranges (P1456R1: Move-only views,[136] P1391R4: Range constructor for std::string_view (constructor from iterator-pair of characters),[137] P1394R4: Range constructor for std::span<ref>,[138] P1870R1: forwarding-range<T> is too subtle[139])
  • Initialization for std::atomic<T> has been changed to make it work with default and list initialization,[140] std::latch and std::barrier can now report the maximum number of threads that the implementation supports through the new member function max()
  • std::weak_equality and std::strong_equality have been removed as they are not used anymore
  • Algorithms in <numeric> have been made constexpr
  • Missing feature-test macros for new or changed features of C 20 have been added[141]

References

[edit]
  1. ^ "The Standard". isocpp.org. Archived from the original on 19 September 2020. Retrieved 7 September 2020.
  2. ^ Sutter, Herb (2019-10-01). "P1000R3: C IS schedule" (PDF). Archived (PDF) from the original on 2019-11-14. Retrieved 2020-02-13.
  3. ^ Dusíková, Hana (2019-11-06). "N4817: 2020 Prague Meeting Invitation and Information" (PDF). Archived (PDF) from the original on 2019-12-29. Retrieved 2020-02-13.
  4. ^ "N4859 Editors' Report -- Programming Languages -- C ". Archived from the original on 2022-12-09. Retrieved 2023-09-22.
  5. ^ "Current Status". isocpp.org. Archived from the original on 8 September 2020. Retrieved 7 September 2020.
  6. ^ "C 20 Approved -- Herb Sutter". isocpp.org. Archived from the original on 11 September 2020. Retrieved 8 September 2020.
  7. ^ "ISO/IEC 14882:2020". Archived from the original on 2020-12-16. Retrieved 2020-12-16.
  8. ^ "Why does the C standard ship every three years?". 13 July 2019. Archived from the original on 13 July 2019. Retrieved 19 July 2019.
  9. ^ "P0592R0: To boldly suggest an overall plan for C 20". Archived from the original on 2017-03-08. Retrieved 2017-05-06.
  10. ^ "P0606R0: Concepts Are Ready" (PDF). Archived (PDF) from the original on 2017-03-28. Retrieved 2017-05-06.
  11. ^ "P1141R1 - Yet another approach for constrained declarations". Archived from the original on 2018-11-11. Retrieved 2018-11-11.
  12. ^ "N4720: Working Draft, Extensions to C for Modules" (PDF). Archived (PDF) from the original on 2019-04-30. Retrieved 2019-04-30.
  13. ^ Tim Shen; Richard Smith. "Designated Initialization Wording". Archived from the original on 2017-10-15. Retrieved 2017-07-16.
  14. ^ Thomas Köppe. "Allow lambda capture [=, this]". Archived from the original on 2019-02-09. Retrieved 2017-07-16.
  15. ^ "Familiar template syntax for generic lambdas". Archived from the original on 2018-11-21. Retrieved 2017-07-16.
  16. ^ "Range-based for statements with initializer". Archived from the original on 2017-04-06. Retrieved 2019-10-30.
  17. ^ a b c "Trip Report: C Standards Meeting in Albuquerque, November 2017". There's Waldo!. 2017-11-20. Archived from the original on 2017-12-11. Retrieved 2017-12-11.
  18. ^ "Wording for lambdas in unevaluated contexts" (PDF). Archived (PDF) from the original on 2017-12-12. Retrieved 2017-12-11.
  19. ^ "Default constructible and assignable stateless lambdas" (PDF). Archived (PDF) from the original on 2017-12-12. Retrieved 2017-12-11.
  20. ^ "Pack expansion in lambda init-capture". www.open-std.org. Archived from the original on 2020-02-14. Retrieved 2017-12-11.
  21. ^ "Class Types in Non-Type Template Parameters" (PDF). www.open-std.org. 2018-06-06. Archived (PDF) from the original on 2022-02-05. Retrieved 2022-02-18.
  22. ^ Nina Ranns; Daveed Vandevoorde. "Down with typename!". Archived from the original on 2018-04-22. Retrieved 2019-05-18.
  23. ^ "Language support for empty objects". Archived from the original on 2018-04-17. Retrieved 2019-08-04.
  24. ^ "Proposed wording for likely and unlikely attributes (Revision 5)". Archived from the original on 2018-05-13. Retrieved 2019-05-18.
  25. ^ "explicit(bool)". www.open-std.org. Archived from the original on 2018-07-20. Retrieved 2018-11-13.
  26. ^ "Allowing Virtual Function Calls in Constant Expressions". www.open-std.org. Archived from the original on 2018-06-11. Retrieved 2019-03-11.
  27. ^ "P1330R0 - Changing the active member of a union inside constexpr". Archived from the original on 2019-07-26. Retrieved 2019-07-26.
  28. ^ "P1002R0 - Try-catch blocks in constexpr functions" (PDF). Archived (PDF) from the original on 2018-11-11. Retrieved 2018-11-11.
  29. ^ "P1327R0 - Allowing dynamic_cast, polymorphic typeid in Constant Expressions". Archived from the original on 2019-07-26. Retrieved 2019-07-26.
  30. ^ "P1006R1 - Constexpr in std::pointer_traits" (PDF). Archived (PDF) from the original on 2018-11-11. Retrieved 2018-11-11.
  31. ^ "P1073R2 - Immediate functions". Archived from the original on 2018-10-26. Retrieved 2018-11-11.
  32. ^ "P1236R0: Alternative Wording for P0907R4 Signed Integers are Two's Complement". Archived from the original on 2018-11-11. Retrieved 2018-11-11.
  33. ^ "P0668R4: Revising the C memory model". Archived from the original on 2018-11-11. Retrieved 2018-11-11.
  34. ^ "P1091R1: Extending structured bindings to be more like variable declarations". www.open-std.org. Archived from the original on 2019-01-26. Retrieved 2019-02-24.
  35. ^ "P1091R2: Extending structured bindings to be more like variable declarations". www.open-std.org. Archived from the original on 2019-01-26. Retrieved 2019-02-24.
  36. ^ "N4649: Working Draft, Technical Specification for C Extensions for Coroutines" (PDF). Archived (PDF) from the original on 2017-05-16. Retrieved 2017-05-06.
  37. ^ a b "P1099R5: Using Enum". www.open-std.org. 2019-07-20. Archived from the original on 2019-08-20. Retrieved 2019-07-20.
  38. ^ a b "P1143R2: Adding the constinit keyword". www.open-std.org. 2019-07-20. Archived from the original on 2019-08-20. Retrieved 2019-07-20.
  39. ^ "P0896R3" (PDF). Archived (PDF) from the original on 2018-11-11. Retrieved 2018-11-11.
  40. ^ "Extending make_shared to Support Arrays". Archived from the original on 2017-09-06. Retrieved 2020-02-12.
  41. ^ Meredith, Alisdair; Sutter, Herb. "Revising atomic_shared_ptr for C 20". JTC1/SC22/WG21 - The C Standards Committee - ISOCPP. ISO. Archived from the original on 4 January 2018. Retrieved 27 December 2018.
  42. ^ "Utility to convert a pointer to a raw pointer". Archived from the original on 2018-02-20. Retrieved 2020-02-12.
  43. ^ Howard E. Hinnant; Tomasz Kamiński. "Extending <chrono> to Calendars and Time Zones". Archived from the original on 2018-05-13. Retrieved 2019-05-18.
  44. ^ Neil MacIntosh; Stephan T. Lavavej. "span: bounds-safe views for sequences of objects". Archived from the original on 2019-05-18. Retrieved 2019-05-18.
  45. ^ Alisdair Meredith; Stephan T. Lavavej (2018-10-04). "Adopt Consistent Container Erasure from Library Fundamentals 2 for C 20". Archived from the original on 2021-03-08. Retrieved 2020-12-14.
  46. ^ Alan Talbot. "<version>". Archived from the original on 2019-05-18. Retrieved 2019-05-18.
  47. ^ "Bit-casting object representations". www.open-std.org. Archived from the original on 2018-08-18. Retrieved 2018-11-10.
  48. ^ "Integrating feature-test macros into the C WD (rev. 2)". www.open-std.org. Archived from the original on 2018-07-20. Retrieved 2018-11-10.
  49. ^ "P1032R1 - Misc constexpr bits". Archived from the original on 2018-10-26. Retrieved 2018-11-11.
  50. ^ "Smart pointer creation with default initialization". Archived from the original on 2019-01-26. Retrieved 2020-02-12.
  51. ^ Mikhail Maltsev. "P0458R2: Checking for Existence of an Element in Associative Containers". Archived from the original on 2022-01-16. Retrieved 2022-01-02.
  52. ^ a b "P0553R4: Bit operations". www.open-std.org. 2019-07-20. Archived from the original on 2019-07-20. Retrieved 2019-07-20.
  53. ^ "P0556R3: Integral power-of-2 operations". www.open-std.org. 2018-06-06. Archived from the original on 2019-06-26. Retrieved 2020-08-08.
  54. ^ "P1355R2 Exposing a narrow contract for ceil2". www.open-std.org. 2019-06-11. Archived from the original on 2019-08-05. Retrieved 2020-08-08.
  55. ^ "On the names of low-level bit manipulation functions" (PDF). www.open-std.org. 2020-02-11. Archived (PDF) from the original on 2020-03-24. Retrieved 2020-08-08.
  56. ^ Tomasz Kamiński (2017-11-09). "Simplified partial function application". Archived from the original on 2020-09-28. Retrieved 2020-11-08.
  57. ^ "C keywords - cppreference.com". en.cppreference.com. Archived from the original on 2012-03-19. Retrieved 2019-08-04.
  58. ^ "explicit specifier - cppreference.com". en.cppreference.com. Archived from the original on 2012-02-21. Retrieved 2019-08-04.
  59. ^ a b c "P1152R4: Deprecating volatile". www.open-std.org. 2019-07-20. Archived from the original on 2019-06-23. Retrieved 2019-07-20.
  60. ^ "attribute specifier sequence(since C 11) - cppreference.com". en.cppreference.com. Archived from the original on 2012-07-05. Retrieved 2019-08-04.
  61. ^ "Working Draft, Standard for Programming Language C (Annex C, §C.1)" (PDF). Archived (PDF) from the original on 2020-04-27. Retrieved 2020-11-18.
  62. ^ a b "P1161R2: Deprecate uses of the comma operator in subscripting expressions". www.open-std.org. Archived from the original on 2019-07-20. Retrieved 2019-07-20.
  63. ^ "C Extensions for Parallelism Version 2". Archived (PDF) from the original on 2022-09-21. Retrieved 2019-07-09.
  64. ^ "C Extensions for Reflection". Archived (PDF) from the original on 2022-09-21. Retrieved 2019-07-09.
  65. ^ "C Extensions for Networking". Archived (PDF) from the original on 2022-09-21. Retrieved 2019-07-09.
  66. ^ Sutter, Herb (2019-07-20). "Trip report: Summer ISO C standards meeting (Cologne)". Sutter's Mill. Archived from the original on 2020-04-17. Retrieved 2019-07-21.
  67. ^ "Reflections on the reflection proposals - Meeting C ". meetingcpp.com. Archived from the original on 2017-06-23. Retrieved 2017-06-30.
  68. ^ "Static reflection". www.open-std.org. Archived from the original on 2020-02-22. Retrieved 2018-11-10.
  69. ^ Herb Sutter. "Metaclasses" (PDF). Archived (PDF) from the original on 2020-11-11. Retrieved 2017-07-23.
  70. ^ "A Unified Executors Proposal for C ". www.open-std.org. Archived from the original on 2020-02-20. Retrieved 2019-02-24.
  71. ^ "N4771: Working Draft, C Extensions for Networking" (PDF). Archived (PDF) from the original on 2020-04-19. Retrieved 2019-03-23.
  72. ^ "ISO/IEC TS 19216:2018 Programming Languages -- C Extensions for Networking". Archived from the original on 2019-01-15. Retrieved 2018-12-17.
  73. ^ "A General Property Customization Mechanism". www.open-std.org. Archived from the original on 2020-01-19. Retrieved 2019-02-24.
  74. ^ "A Unified Futures Proposal for C ". Archived from the original on 2022-09-21. Retrieved 2019-07-08.
  75. ^ "C compiler support - cppreference.com". en.cppreference.com. Archived from the original on 2022-08-08. Retrieved 2022-08-12.
  76. ^ jawiddis. "Visual Studio 2019 version 16.10 Release Notes". docs.microsoft.com. Archived from the original on 2021-08-11. Retrieved 2021-07-13.
  77. ^ "MSVC C 20 and the /std:c 20 Switch". docs.microsoft.com. 2 September 2021. Archived from the original on 2021-09-06. Retrieved 2021-09-07.
  78. ^ Visual Studio documentation for Microsoft C , Microsoft Docs, 2022-04-19, archived from the original on 2022-04-19, retrieved 2022-04-19
  79. ^ "Visual Studio 2019 Compatibility". docs.microsoft.com. Archived from the original on 2020-06-03. Retrieved 2022-08-12.
  80. ^ "Clang - C Programming Language Status". clang.llvm.org. Archived from the original on 2013-07-04. Retrieved 2022-04-19.
  81. ^ "C compiler support - cppreference.com". en.cppreference.com. Archived from the original on 2020-10-03. Retrieved 2020-10-10.
  82. ^ "Andrew Sutton - [PATCH] Add -std=c 2a". gcc.gnu.org. Archived from the original on 2021-03-01. Retrieved 2022-04-19.
  83. ^ "C Standards Support in GCC - GNU Project". gcc.gnu.org. Archived from the original on 2022-04-20. Retrieved 2022-04-19.
  84. ^ Herb Sutter (15 July 2017). "Trip report: Summer ISO C standards meeting (Toronto)". Archived from the original on 2017-08-06. Retrieved 2017-07-16.
  85. ^ Andrew Sutton; Bjarne Stroustrup (2013-02-24). "Concepts Lite: Constraining Templates with Predicates". isocpp.org. Archived from the original on 2021-01-16. Retrieved 2021-01-13.
  86. ^ Herb Sutter (11 November 2017). "Trip report: Fall ISO C standards meeting (Albuquerque)". Archived from the original on 2019-02-13. Retrieved 2017-12-04.
  87. ^ Smith, Richard; Perchik, Dawn; Köppe, Thomas. "N4714 Editors' Report -- Programming Languages -- C ". C standards drafts. GitHub. Archived from the original on 21 September 2022. Retrieved 27 December 2018.
  88. ^ Botond Ballo (28 March 2018). "Trip Report: C Standards Meeting in Jacksonville, March 2018". Archived from the original on 2019-05-18. Retrieved 2019-05-18.
  89. ^ Herb Sutter (2 July 2018). "Trip report: Summer ISO C standards meeting (Rapperswil)". Archived from the original on 2020-05-23. Retrieved 2018-11-10.
  90. ^ "Support for contract based programming in C ". www.open-std.org. Archived from the original on 2020-01-15. Retrieved 2018-11-10.
  91. ^ fall meeting in November 2018
  92. ^ "P1289R0 - Access control in contract conditions" (PDF). Archived (PDF) from the original on 2018-11-11. Retrieved 2018-11-11.
  93. ^ winter meeting in February 2019
  94. ^ "r/cpp - 2019-02 Kona ISO C Committee Trip Report (C 20 design is complete; Modules in C 20; Coroutines in C 20; Reflection TS v1 published; work begins on a C Ecosystem Technical Report)". reddit. 23 February 2019. Archived from the original on 2019-02-23. Retrieved 2019-02-24.
  95. ^ "Trip report: Winter ISO C standards meeting (Kona)". Sutter's Mill. 2019-02-23. Archived from the original on 2019-02-24. Retrieved 2019-02-24.
  96. ^ "2019 Cologne Meeting Invitation and Information" (PDF).
  97. ^ "r/cpp - 2019-07 Cologne ISO C Committee Trip Report — 🚀 The C 20 Eagle has Landed 🚀 (C 20 Committee Draft shipped; Contracts Moved From C 20 to a Study Group; 'std::format' in C 20; C 20 Synchronization Library)". reddit. 20 July 2019. Archived from the original on 2020-04-20. Retrieved 2019-09-15.
  98. ^ Botond Ballo (26 July 2019). "Trip Report: C Standards Meeting in Cologne, July 2019". Archived from the original on 2020-02-26. Retrieved 2019-08-05.
  99. ^ Sutter, Herb (20 July 2019). "Trip report: Summer ISO C standards meeting (Cologne)". Archived from the original on 2020-04-17. Retrieved 2019-07-21.
  100. ^ Josuttis, Nicolai. "P1823R0: Remove Contracts from C 20" (PDF). Archived (PDF) from the original on 2020-08-13. Retrieved 2019-08-20.
  101. ^ "Permitting trivial default initialization in constexpr contexts" (PDF). Archived (PDF) from the original on 2020-10-19. Retrieved 2019-07-20.
  102. ^ "P1668R1: Enabling Constexpr Intrinsics By Permitting Unevaluated inline-asm in Constexpr Functions". www.open-std.org. Archived from the original on 2020-01-19. Retrieved 2019-07-20.
  103. ^ "P1186R3: When do you actually use <=>?". www.open-std.org. 2019-07-20. Archived from the original on 2019-08-20. Retrieved 2019-07-20.
  104. ^ "P1630R1: Spaceship needs a tune-up". www.open-std.org. 2019-07-20. Archived from the original on 2019-08-20. Retrieved 2019-07-20.
  105. ^ "P1766R1: Mitigating minor modules maladies". www.open-std.org. 2019-07-20. Archived from the original on 2019-08-20. Retrieved 2019-07-20.
  106. ^ "P1452R2: On the non-uniform semantics of return-type-requirements". www.open-std.org. 2019-07-20. Archived from the original on 2019-08-20. Retrieved 2019-07-20.
  107. ^ "P1771R1: nodiscard for constructors" (PDF). www.open-std.org. 2019-07-20. Archived (PDF) from the original on 2022-09-21. Retrieved 2019-07-20.
  108. ^ "P1754R1: Rename concepts to standard_case for C 20, while we still can" (PDF). www.open-std.org. 2019-07-20. Archived (PDF) from the original on 2019-08-20. Retrieved 2019-07-20.
  109. ^ "P0645R10: Text Formatting". www.open-std.org. 2019-07-20. Archived from the original on 2019-08-20. Retrieved 2019-07-20.
  110. ^ "std::format in C 20". www.zverovich.net. 2019-07-23. Archived from the original on 2019-07-23. Retrieved 2019-09-15.
  111. ^ "P1361R2: Integration of chrono with text formatting" (PDF). www.open-std.org. 2019-07-20. Archived (PDF) from the original on 2019-08-20. Retrieved 2019-07-20.
  112. ^ "P1652R1: Printf corner cases in std::format". www.open-std.org. 2019-07-20. Archived from the original on 2019-08-20. Retrieved 2019-07-20.
  113. ^ "P1965R2: constexpr INVOKE". www.open-std.org. 2019-07-20. Archived from the original on 2019-08-20. Retrieved 2019-07-20.
  114. ^ "P0631R8: Math Constants" (PDF). www.open-std.org. 2019-07-20. Archived (PDF) from the original on 2019-08-20. Retrieved 2019-07-20.
  115. ^ "P1643R1: Add wait/notify to atomic_ref<T>". www.open-std.org. 2019-07-20. Archived from the original on 2019-08-20. Retrieved 2019-07-20.
  116. ^ "P1664R0: Add wait/notify to atomic<shared_ptr<T>>". www.open-std.org. 2019-07-20. Archived from the original on 2021-11-05. Retrieved 2019-07-20.
  117. ^ "P1614R2: The Mothership has Landed - Adding <=> to the Library". www.open-std.org. 2019-07-20. Archived from the original on 2019-08-20. Retrieved 2019-07-20.
  118. ^ "P1502R1: Standard library header units for C 20". www.open-std.org. 2019-07-20. Archived from the original on 2019-08-20. Retrieved 2019-07-20.
  119. ^ "P1135R6: The C 20 Synchronization Library". www.open-std.org. 2019-07-20. Archived from the original on 2019-08-20. Retrieved 2019-07-20.
  120. ^ "P0514R4: Efficient concurrent waiting for C 20" (PDF). Archived (PDF) from the original on 2018-08-18. Retrieved 2019-07-20.
  121. ^ "P0666R2: Revised Latches and Barriers for C 20" (PDF). Archived (PDF) from the original on 2018-08-18. Retrieved 2019-07-20.
  122. ^ "P0995R1: Improving atomic_flag". Archived from the original on 2019-07-20. Retrieved 2019-07-20.
  123. ^ "P1285R0: Don't Make C Unimplementable On Small CPUs". Archived from the original on 2019-07-15. Retrieved 2019-07-20.
  124. ^ "P1208R6: Adopt source_location from Library Fundamentals V3 for C 20" (PDF). Archived (PDF) from the original on 2019-08-20. Retrieved 2019-08-20.
  125. ^ "P0980R1: Making std::string constexpr" (PDF). Archived (PDF) from the original on 2020-09-29. Retrieved 2020-07-30.
  126. ^ "P1004R2: Making std::vector constexpr" (PDF). Archived (PDF) from the original on 2020-09-28. Retrieved 2020-07-30.
  127. ^ "P0660R10: Stop Token and Joining Thread" (PDF). Archived (PDF) from the original on 2019-08-20. Retrieved 2019-08-20.
  128. ^ fall meeting in November 2019
  129. ^ "r/cpp - 2019-11 Belfast ISO C Committee Trip Report — Started Processing Feedback on the C 20 Committee Draft; ABI Review Group Formed". reddit. 9 November 2019. Archived from the original on 2019-11-09. Retrieved 2019-11-09.
  130. ^ Sutter, Herb (2019-11-09). "Trip report: Autumn ISO C standards meeting (Belfast)". Sutter's Mill. Archived from the original on 2019-11-09. Retrieved 2019-11-09.
  131. ^ botondballo (2019-11-15). "Trip Report: C Standards Meeting in Belfast, November 2019". There's Waldo!. Archived from the original on 2019-11-20. Retrieved 2019-11-24.
  132. ^ "P1907R0: Inconsistencies with non-type template parameters". www.open-std.org. 2019-10-07. Archived from the original on 2019-11-09. Retrieved 2019-11-09.
  133. ^ "P1714: NTTP are incomplete without float, double, and long double! (Revision 1)". www.open-std.org. 2019-07-19. Archived from the original on 2019-11-09. Retrieved 2019-11-09.
  134. ^ "P1855R=: Make <compare> freestanding". www.open-std.org. 2019-10-05. Archived from the original on 2019-11-09. Retrieved 2019-11-09.
  135. ^ "P1872R0: span should have size_type not index_type" (PDF). www.open-std.org. 2019-09-16. Archived (PDF) from the original on 2019-11-09. Retrieved 2019-11-09.
  136. ^ "P1456: Move-only views" (PDF). www.open-std.org. 2019-01-25. Archived (PDF) from the original on 2019-11-09. Retrieved 2019-11-09.
  137. ^ "P1391: Range constructor for std::string_view" (PDF). www.open-std.org. Archived (PDF) from the original on 2020-01-04. Retrieved 2019-11-09.
  138. ^ "P1394: Range constructor for std::span" (PDF). www.open-std.org. 2019-08-02. Archived (PDF) from the original on 2019-11-09. Retrieved 2019-11-09.
  139. ^ "P1870R1: forwarding-range<T> is too subtle". www.open-std.org. 6 October 2019. Archived from the original on 2019-11-09. Retrieved 2019-11-09.
  140. ^ "P0883: Fixing Atomic Initialization" (PDF). www.open-std.org. 2018-06-05. Archived (PDF) from the original on 2019-11-09. Retrieved 2019-11-09.
  141. ^ "Missing feature-test macros 2018-2019". www.open-std.org. 2019-10-06. Archived from the original on 2019-11-09. Retrieved 2019-11-09.
[edit]
Retrieved from "https://en.wikipedia.org/w/index.php?title=C++20&oldid=1257255539"